Knowledge
A flange type is defined by how it joins the pipe: weld neck, slip-on, lap joint, threaded, or blind. Match the joint to pressure, temperature, inspection needs, and how often the line will be opened.
ASTM A182 · ASME B16.5 · Class 150 / 300
Reviewed by JNDIA engineering · Updated September 2026
Comparison
The table below compares the five faces JNDIA machines most often. Welding neck is the high-integrity default; slip-on and threaded trade strength for fit-up; lap joint is for frequent opening; blind closes the line.
| Type | Code | Connection | Typical service | Catalog |
|---|---|---|---|---|
| Weld neck | WN / RF | Butt-welded tapered hub | High pressure, high temperature, cyclic | View products |
| Slip-on | SO / RF | Pipe slips in; fillet welds both sides | Low to moderate pressure, easier alignment | View products |
| Lap joint | LJ | Loose ring over a stub end | Frequent opening; mixed-grade rings | View products |
| Threaded | THRD / RF | Screws onto threaded pipe, no weld | Smaller sizes, utility, weld-restricted areas | View products |
| Blind | BL / RF | Solid disc, no bore | Isolation, vessel openings, hydrotest | View products |
| Socket weld | SW / RF | Pipe into socket, fillet weld at hub | Small high-pressure lines | View products |
FAQ
The common ASME B16.5 types are weld neck, slip-on, lap joint, threaded, socket weld, and blind. Weld neck is preferred for demanding service; blind closes a line; slip-on and threaded are used where pressure is lower.
A weld neck flange is the usual choice for high pressure, high temperature, and cyclic duty because the tapered hub and matching bore move stress away from the gasket face.
JNDIA supplies stainless steel weld neck, slip-on, blind, socket weld, and threaded flanges in 304L and 316L, Class 150 and 300, typically 1/2" through 24", to ASME B16.5 / ASTM A182.